Bang Energy recently tried to trademark the phrase Purple Rain with the US Patent and Trademark Office but lost after an objection by the estate of Prince the legendary pop singer. A forum of justices said the phrase “uniquely and unmistakably” points to the singer.
In this case i think even a casual observer would tie the phrase to Prince. Apart from the great Purple Rain song there is also the 1984 musical movie of the same name. A side note if you haven’t seen the movie usually this type of movie isn’t great but Prince’s “Purple Rain” is a fast paced movie if amazing music with Prince at his prime.